Scary discussion on using Shellac
Posted: Wed 01 Dec, 2021 2:20 pm
Let's see if we can explain how to use shellac without making it sound too high falutin'.
Shellac is great stuff in that it can be painted over nearly everything - bare wood, painted wood, even waxed wood. It is a varnish, very fast drying and finishes to a beautiful glassy polish if applied correctly.
Most people will understand that shellac is constituent to French Polishing. That is where experienced craftsmen can build up a beautiful polish on tables and furniture using a 'cotton rubber' to create a high gloss finish.
You can also do that on a picture frame, but that is best left to a more zealous enthusiast.
For a framer using relatively narrow mouldings, the shellac can be easily painted on with a dedicated brush.
And there are two types of brush to choose from.
One is a Squirrel Hair Polishing Mop and this is best suited to wide flat mouldings. In using this brush, the operator will soak it in shellac, press out the excess polish with gloved fingers and shape the brush into a wide chisel. When pulled slowly across the moulding, the shellac will form a smooth wet varnish completely free of any brush marks.
The only downside here is the price, The most useful brush size, no.10 is £50 or so.
A cheaper alternative is to use a flat 3/4" 'One Stroke' watercolour brush. A Pro Art Prolene is a good reliable brand. This will serve well on narrower mouldings.
Now if it's just to paint on a coat of shellac to act as a barrier, then any sort of brush will do the trick but if the idea is to achieve a flat faultless finish, then the quality of the brush equals the quality of the finish.
One reason to note is that shellac dries within seconds, so that unlike oil varnishes, the brush marks do not have any time to level out.
The shellac finish most people will be familiar with is Shellac Sanding Sealer.
This product is basically a strong solution of transparent shellac with a soapy like solid called Zinc Stearate floating about in it.
The zinc stearate is quite translucent in the polish and is released as a white powdery deposit when the sealer is sanded.
Because the powder is quite slippery, it lubricates the sand paper and prevents it tearing into the polish.
Sanding sealer provides an excellent base foundation for any finish on bare wood. The zinc powder also contributes to a degree of grain filling.
To use the sealer best, brush on two coats, allowing 15min drying time between.
After allowing the sealer to dry hard, best over-night, sand back the surface of the sealer flat with 600grit wet n'dry.
Doing this will release the zinc and result in a white powdery deposit on the polish.
DO NOT press down hard with the sand paper. Let the grit in the paper do all the work. The paper should fill up with white zinc only. If you see streaks of melted polish on the paper then you are pressing too hard and tearing into the finish.
When you're finished with that, all you need to do is wipe the powder away with a cotton pad and you should have a dull matt but perfectly smooth layer of polish.
If the shellac sealer has been painted over bare-wood which has been stained and topped with a glaze of earth pigments, then rubbing on two coats of wax will give a lovely finish with a good depth of colour.
A note of caution is not to buy Sanding Sealer from building supplies like Screw Fix or other. These are construction grade only and are adulterated with synthetic resins. Use the more familiar brand like Liberon.
The next post moves on to using Shellac Polish and mixing in with earth pigments and spirit stains.
Shellac is great stuff in that it can be painted over nearly everything - bare wood, painted wood, even waxed wood. It is a varnish, very fast drying and finishes to a beautiful glassy polish if applied correctly.
Most people will understand that shellac is constituent to French Polishing. That is where experienced craftsmen can build up a beautiful polish on tables and furniture using a 'cotton rubber' to create a high gloss finish.
You can also do that on a picture frame, but that is best left to a more zealous enthusiast.
For a framer using relatively narrow mouldings, the shellac can be easily painted on with a dedicated brush.
And there are two types of brush to choose from.
One is a Squirrel Hair Polishing Mop and this is best suited to wide flat mouldings. In using this brush, the operator will soak it in shellac, press out the excess polish with gloved fingers and shape the brush into a wide chisel. When pulled slowly across the moulding, the shellac will form a smooth wet varnish completely free of any brush marks.
The only downside here is the price, The most useful brush size, no.10 is £50 or so.
A cheaper alternative is to use a flat 3/4" 'One Stroke' watercolour brush. A Pro Art Prolene is a good reliable brand. This will serve well on narrower mouldings.
Now if it's just to paint on a coat of shellac to act as a barrier, then any sort of brush will do the trick but if the idea is to achieve a flat faultless finish, then the quality of the brush equals the quality of the finish.
One reason to note is that shellac dries within seconds, so that unlike oil varnishes, the brush marks do not have any time to level out.
The shellac finish most people will be familiar with is Shellac Sanding Sealer.
This product is basically a strong solution of transparent shellac with a soapy like solid called Zinc Stearate floating about in it.
The zinc stearate is quite translucent in the polish and is released as a white powdery deposit when the sealer is sanded.
Because the powder is quite slippery, it lubricates the sand paper and prevents it tearing into the polish.
Sanding sealer provides an excellent base foundation for any finish on bare wood. The zinc powder also contributes to a degree of grain filling.
To use the sealer best, brush on two coats, allowing 15min drying time between.
After allowing the sealer to dry hard, best over-night, sand back the surface of the sealer flat with 600grit wet n'dry.
Doing this will release the zinc and result in a white powdery deposit on the polish.
DO NOT press down hard with the sand paper. Let the grit in the paper do all the work. The paper should fill up with white zinc only. If you see streaks of melted polish on the paper then you are pressing too hard and tearing into the finish.
When you're finished with that, all you need to do is wipe the powder away with a cotton pad and you should have a dull matt but perfectly smooth layer of polish.
If the shellac sealer has been painted over bare-wood which has been stained and topped with a glaze of earth pigments, then rubbing on two coats of wax will give a lovely finish with a good depth of colour.
A note of caution is not to buy Sanding Sealer from building supplies like Screw Fix or other. These are construction grade only and are adulterated with synthetic resins. Use the more familiar brand like Liberon.
The next post moves on to using Shellac Polish and mixing in with earth pigments and spirit stains.